pdfviewer: make pdfviewer compile on mac

Review URL: https://codereview.chromium.org/23163007

git-svn-id: http://skia.googlecode.com/svn/trunk@10721 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/experimental/PdfViewer/chop_transparency_main.cpp b/experimental/PdfViewer/chop_transparency_main.cpp
index c9a199c..f887ab3 100644
--- a/experimental/PdfViewer/chop_transparency_main.cpp
+++ b/experimental/PdfViewer/chop_transparency_main.cpp
@@ -39,7 +39,7 @@
     { SkImageEncoder::kWEBP_Type, SkImageDecoder::kWEBP_Format, ".webp" }
 };
 
-SkISize opaqueSize(const SkBitmap& bm) {
+static SkISize opaqueSize(const SkBitmap& bm) {
     int width = 1;
     int height = 1;
     for (int y = 0 ; y < bm.height(); y++) {